I am not aware that Ancestry.com does YDNA testing of the same type that FTDNA does. You seem to believe otherwise. In any case, I am having difficulty with the logic of your premise given the facts:
FTDNA used to support Y-Search to allow comparison of YDNA tests from all providers (similar to GEDMATCH.COM) but now they don't because they (arrogantly) conclude there are no other YDNA test providers who matter. Since Ancestry.com never did YDNA tests in the first place and, as far as I know, still don't, I do not understand what profit motives FTDNA would have in forcing people to buy another test from Ancestry.com.
Please help me understand if I have missed the gist of your point, because, right now, it makes no sense to me.